As wireless communication develops, a requirement for a microwave filter increases. To meet different application environments, different filter structures appear. A tunable cavity filter is widely applied to a communications system due to its features such as a low passband insertion loss, high stopband inhibition, tuning convenience, and a relative high power processing capacity.
For an E-plane filter, by means of precision control over a diaphragm, a frequency adjustment screw and a coupling adjustment screw may be cancelled, and commissioning of the filter is not required, which helps implement a tunable structure of a high-frequency microwave filter. A structure of an E-plane filter in the prior art is: a metal plate and a dielectric slice are disposed inside a rectangular waveguide tube, and a motor is used to drive the dielectric slice to move, to change a relative position relationship between the dielectric slice and the metal plate, so as to adjust a frequency of the filter. However, the dielectric slice in the structure of this type of E-plane filter is in an integral sheet-like structure, the dielectric slice stretches across a resonant cavity inside the rectangular waveguide tube of the filter, and the dielectric slice has a very low requirement for a dielectric constant. Such a dielectric slice has a very small thickness, is hard in manufacturing, and is poor in process reliability. In addition, because the dielectric slice has relatively weak hardness, a shock resistance capability is poor when the dielectric slice is assembled in the E-plane filter. Because a shock of the E-plane filter easily causes a position change of the dielectric slice, performance of the E-plane filter is affected. As a result, a frequency and performance of the E-plane filter are unstable.